Falling Blocks with Normal Blocks

So, when I was messing around with falling blocks in the 1.17 20w46a Snapshot, the most recent at this point, I used a falling block command to hide lighting, it was glitching the whole block, but not the top, I then tried to use it in 1.16.4, (I used gray concrete for placing the block, and for the command) and the gray_concrete, combines with the falling gray_concrete to make it disappear. But not only that, but it glitches out as well. But when I move the falling block, it somehow duplicates, but the duplication is still a falling block, after around 30 seconds, the block drops like apples falling from a tree. Currently I can't post the screenshots to you, but if you try yourself, you should get the same results

This is the command I used... summon falling_block -238 22 196 {NoGravity:1,Time:0,BlockState:{Name:"gray_concrete"}}